There are reports on (1)-7-phenylpyrazolo[1,5-a]pyridine derivatives and a method for producing the same (see Patent Documents 1 and 2), (2) 7-phenylpyrazolopyrimidine derivatives and a method for producing the same (see Patent Document 3) and (3) 7-phenylpyrazolotriazine derivatives and a method for producing the same (see Patent Document 4), which have a CRF receptor antagonistic action and expected as a therapeutic agent for depression, anxiety and the like.
Regarding a step of a halogenating reaction and a step of an amino group introducing reaction in the methods for producing pyrazole-fused ring derivatives (7-phenylpyrazolo[1,5-a]pyridine derivatives and the like) described in the documents, the following points are mentioned as problems in the case of use for industrial production.
(1) In the step of a halogenating reaction, purification by column chromatography is used after reaction.
(2) In the step of a halogenating reaction, 1,2-diiodoethane which is not so suitable for industrial production is used as a halogenating reagent.
(3) Regarding the step of a halogenating reaction, there is a lot of examples showing a yield of 60 to 70% in an iodination reaction of a pyrazolo[1,5-a]pyridine derivative using 1,2-diiodoethane, revealing unsatisfactory yields. (see Patent Document 2)
(4) In the step of introducing an amino group into a pyrazole-fused ring derivative (pyrazolo[1,5-a]pyridine ring and the like), a reduction reaction-alkylation reaction after a nitration reaction is used or a Crutius reaction from a carboxylic acid derivative is used; however, these reactions show poor yields and reaction steps thereof are long. Further, a 3-aminopyrazopyridine compound which is an intermediate in these reactions is unstable, and is not suitable as an intermediate in an industrial synthesis method.
Taking the above-described points into consideration, the production methods described in the documents are not satisfactory as an industrial production method.
A compound represented by following formula, which is a 7-iodopyrazolo[1,5-a]pyridine derivative or a salt thereof, or a solvate thereof, is a novel compound and is not known until now.
[Regarding Iodination Reaction]
Although pentafluoroiodobenzene is a known compound, there is no example using pentafluoroiodobenzene as a reagent in an iodination reaction. Regarding an iodination reaction step of a pyrazole-fused ring derivative (pyrazolo[1,5-a]pyridine derivative and the like), it is reported that n-butyllithium and 1,2-diiodoethane as described above (see Patent Documents 1 and 2) were used.
[Regarding an Amidation Reaction by a Coupling Reaction to a Bi-cyclic Heteroaromatic Compound]
Regarding a reaction for amidating an aryl halide using a copper catalyst, Buchwald et al. made a report (see Non-Patent Document 1). However, there is known no amidation reaction by a coupling reaction to a bi-cyclic heteroaromatic compound such as pyrazolo[1,5-a]pyridine and the like.    Patent Document 1: International Publication No. 02/088121, pamphlet.    Patent Document 2: International Publication No. 03/078435, pamphlet.    Patent Document 3: International Publication No. 00/59908, pamphlet.    Patent Document 4: International Publication No. 00/59907, pamphlet.    Non-Patent Document 1: J. Am. Chem. Soc., 7421-7428, 124, 2002.